"Police will tell you that they're wanting to refer people to help, but that help simply isn't there.
"Fundamentally, if we want to get on top of the problem, we have to address the demand for drugs, rather than the supply. The best way to do that is to put money into prevention, education, treatment and rehabilitation."
Class A drug convictions - covering supply, manufacturing and possession - had also considerably increased in smaller New Zealand centres.
Salvation Army managing director for addiction, Lynette Hutson, said "police are probably fighting a tidal wave".
"It's very difficult for them to keep responding to something that's now become so normalised and widespread across society."
Police and social services needed to work closer together, Hutson said.
"What we really need is to increase the treatment options and to make it more accessible for people to get treatment earlier, rather than later."
Areas north of Auckland also had a growing number of Class A convictions, from 52 in Whangarei in 2007, to 309 in 2016.
Convictions in Kaikohe - which has a population of just under 4000 - increased from 16 in 2007, to a peak of 70 in 2013. There were 44 last year.
Far North District councillor Colin Kitchen said methamphetamine abuse was closely linked to poverty.
"I feel sorry for some of these people. We need to get help for them, and we need more police and people trying to prevent this sort of thing."
Kitchen - a member of the Northland District Health Board and a chief fire officer - said drug users were putting a strain on emergency services.
"We have people high on drugs abusing our staff. Something is really wrong with our society; we need something done about it."
In other areas, total Class A convictions in Nelson jumped from 11 in 2007, to 74 in 2016.
In Palmerston North, there were 24 in 2007, rising to 121 in 2016.
Convictions related to cocaine and heroin were relatively low in the 2007 to 2016 period, totalling 214 and 97 respectively.
LSD convictions totalled 822.
